This invention relates to the field of data compression. More particularly, this invention relates to the field of video image compression. More particularly still, this invention relates to the field of holographic optical correlation and the application of holographic optical correlation in a feedback loop to produce compression of video images.
It is well known to take advantage of the speed and efficiency of computer hardware and algorithms to perform digital transforms for data compression of video images. However, analog transformation remains an important alternative to digital processing in certain applications. These applications may include optical computing, crystallography, interferometry, image acquisition, and image processing.
In many cases where the input image is accessible or available, operations such as convolution, smoothing, or image enhancement can be performed faster optically than digitally, and can take advantage of the distribution of information in the transformed domain.
A preferred method of transforming or compressing image data is the use of the Fourier transform of a real, two-dimensional input. A disadvantage of the Fourier transform is that a Fourier transform for transforming real two-dimensional inputs, is redundant. The Fourier transform encodes information in terms of both magnitude and phase over one-half of the output plane and repeats it in conjugate form over the other half. Recording devices such as photographic film, photo detectors, and photo diodes respond only to intensity and therefore half of the information contained in the transform is lost or unnecessary.
In applications where the transform phase is important, two broad classes of solutions have been used. In the first class of solutions phase is deduced from intensity-only records. For example, computer algorithms which transform from one domain to the other and back again can sometimes converge on a solution when constraints such as non-negativity and finite support are applied. In a second class of solutions, defracted radiation is modified so that the phase is encoded in the intensity, thereby rendering magnitude-only records sufficient for inverting the transform. Examples include phase contrast microscopy, the central dark ground method, and holography.
A major disadvantage of conventional digital image processing or digital image compression is that the computations for carrying out real-time video image processing or image compression are highly resource intensive when using conventional sequential digital processors, and places undesirable limits on achievable compression rates and image quality. The conventional digital processor carries out the computations in a serial manner, i.e., one computation after another. Although these computations are rapid and the speed and efficiency of computing hardware is a increasing everyday, so are the demands for real-time high resolution video signaling over limited bandwidth channels. Further, the number of computations required in a typical digital processing compression technique is proportional to the pixelation of the video image.
Thus, there is a need and desire for a method of carrying out video image processing and video image compression using holographic processing techniques. Holographic techniques gain the advantage of parallel processing of video images as opposed to the serial processing carried out in traditional digital image processing and digital image compression.
Further, there is a need and desire for a method and apparatus for image processing and image compression that relies on electro-optical systems to produce the image processing or image compression results, thereby taking advantage of the rapid processing speed inherent in optical processing techniques.
The present invention relates to a method of compressing data. The method includes resolving data into a coherent optical image, presenting the optical image to a holographic medium having stored images, determining a best match between the presented image/image component and the stored image components, the best match being a correlated image, and communicating data representative of the correlated image.
The present invention further relates to a system for compressing a video image. The system includes a processor, an image display coupled to the processor, and a holographic medium having a plurality of stored images. The holographic medium is in optical communication with the image display. Also, the system includes a detector array in optical communication with the holographic medium and an output register coupled to the detector array.
The present invention still further relates to a system for communicating data between two points. The system includes a data compression system, a communication channel coupled to the data compression system, and a data decompression system coupled to the communication channel. The data compression system includes a processor, an optical spatial light modulator (SLM) device coupled to the processor, a holographic medium in optical communication with the SLM, and a detection array in optical communication with the holographic medium.